During BODC quality control, data were screened using in house visualisation software. The data were screened and any obvious outliers and spikes were looked at in closer detail and flagged if necessary. The originator provided quality flags for all data and so minimal flags were added during BODC processing as data had already been through originator QC. The originator's flags were converted to 'L' flags during processing.

There were a number of profiles where CPHLZZXX and CPHLPR01 are negative for the duration of the cast and so the whole of these casts have been flagged 'M'.

CCOMD002

The first cycle of the series 1886252 has the value -95.292503 ppb which was flagged by the originator. During BODC processing this value was set to null.

Open Data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

If the Information Provider does not provide a specific attribution statement, or if you are using Information from several Information Providers and multiple attributions are not practical in your product or application, you may consider using the following:

"Contains public sector information licensed under the Open Government Licence v1.0."

Sea-Bird Dissolved Oxygen Sensor SBE 43 and SBE 43F

The SBE 43 is a dissolved oxygen sensor designed for marine applications. It incorporates a high-performance Clark polarographic membrane with a pump that continuously plumbs water through it, preventing algal growth and the development of anoxic conditions when the sensor is taking measurements.

Two configurations are available: SBE 43 produces a voltage output and can be incorporated with any Sea-Bird CTD that accepts input from a 0-5 volt auxiliary sensor, while the SBE 43F produces a frequency output and can be integrated with an SBE 52-MP (Moored Profiler CTD) or used for OEM applications. The specifications below are common to both.

Sea-Bird Electronics SBE 911 and SBE 917 series CTD profilers

The SBE 911 and SBE 917 series of conductivity-temperature-depth (CTD) units are used to collect hydrographic profiles, including temperature, conductivity and pressure as standard. Each profiler consists of an underwater unit and deck unit or SEARAM. Auxiliary sensors, such as fluorometers, dissolved oxygen sensors and transmissometers, and carousel water samplers are commonly added to the underwater unit.

Underwater unit

The CTD underwater unit (SBE 9 or SBE 9 plus) comprises a protective cage (usually with a carousel water sampler), including a main pressure housing containing power supplies, acquisition electronics, telemetry circuitry, and a suite of modular sensors. The original SBE 9 incorporated Sea-Bird's standard modular SBE 3 temperature sensor and SBE 4 conductivity sensor, and a Paroscientific Digiquartz pressure sensor. The conductivity cell was connected to a pump-fed plastic tubing circuit that could include auxiliary sensors. Each SBE 9 unit was custom built to individual specification. The SBE 9 was replaced in 1997 by an off-the-shelf version, termed the SBE 9 plus, that incorporated the SBE 3 plus (or SBE 3P) temperature sensor, SBE 4C conductivity sensor and a Paroscientific Digiquartz pressure sensor. Sensors could be connected to a pump-fed plastic tubing circuit or stand-alone.

Temperature, conductivity and pressure sensors

The conductivity, temperature, and pressure sensors supplied with Sea-Bird CTD systems have outputs in the form of variable frequencies, which are measured using high-speed parallel counters. The resulting count totals are converted to numeric representations of the original frequencies, which bear a direct relationship to temperature, conductivity or pressure. Sampling frequencies for these sensors are typically set at 24 Hz.

The temperature sensing element is a glass-coated thermistor bead, pressure-protected inside a stainless steel tube, while the conductivity sensing element is a cylindrical, flow-through, borosilicate glass cell with three internal platinum electrodes. Thermistor resistance or conductivity cell resistance, respectively, is the controlling element in an optimized Wien Bridge oscillator circuit, which produces a frequency output that can be converted to a temperature or conductivity reading. These sensors are available with depth ratings of 6800 m (aluminium housing) or 10500 m (titanium housing). The Paroscientific Digiquartz pressure sensor comprises a quartz crystal resonator that responds to pressure-induced stress, and temperature is measured for thermal compensation of the calculated pressure.

Additional sensors

Optional sensors for dissolved oxygen, pH, light transmission, fluorescence and others do not require the very high levels of resolution needed in the primary CTD channels, nor do these sensors generally offer variable frequency outputs. Accordingly, signals from the auxiliary sensors are acquired using a conventional voltage-input multiplexed A/D converter (optional). Some Sea-Bird CTDs use a strain gauge pressure sensor (Senso-Metrics) in which case their pressure output data is in the same form as that from the auxiliary sensors as described above.

Deck unit or SEARAM

Each underwater unit is connected to a power supply and data logging system: the SBE 11 (or SBE 11 plus) deck unit allows real-time interfacing between the deck and the underwater unit via a conductive wire, while the submersible SBE 17 (or SBE 17 plus) SEARAM plugs directly into the underwater unit and data are downloaded on recovery of the CTD. The combination of SBE 9 and SBE 17 or SBE 11 are termed SBE 917 or SBE 911, respectively, while the combinations of SBE 9 plus and SBE 17 plus or SBE 11 plus are termed SBE 917 plus or SBE 911 plus.

Aquatracka fluorometer

The Chelsea Instruments Aquatracka is a logarithmic response fluorometer. It uses a pulsed (5.5 Hz) xenon light source discharging between 320 and 800 nm through a blue filter with a peak transmission of 420 nm and a bandwidth at half maximum of 100 nm. A red filter with sharp cut off, 10% transmission at 664 nm and 678 nm, is used to pass chlorophyll-a fluorescence to the sample photodiode.

The instrument may be deployed either in a through-flow tank, on a CTD frame or moored with a data logging package.

WETLabs ECO FLNTU fluorescence and turbidity sensor

The Environmental Characterization Optics (ECO) Fluorometer and Turbidity (FLNTU) sensor is a dual wavelength, single-angle instrument that simultaneously determines chlorophyll fluorescence and turbidity. It is easily integrated in CTD packages and provides a reliable turbidity measurement that is not affected by Colored Dissolved Organic Matter (CDOM) concentration.

The FLNTU can operate continuously or periodically and has two different types of connectors to output the data. There are 5 other models that operate the same way as this instrument but have slight differences, as stated below:

FLNTU(RT) - has an analog an RS-232 serial output and operates continuously, when power is supplied

FLNTU(RT)D - similar to the FLNTU(RT) but has a depth rating of 6000 m

FLNTUB - has internal batteries for autonomous operation

FLNTUS - has an integrated anti-fouling bio-wiper

FLNTUSB - has the same characteristics as the FLNTUS but with internal batteries for autonomous operation

WETLabs ECO-FL Fluorometer

The Environmental Characterization Optics series of single channel fluorometers are designed to measure concentrations of natural and synthetic substances in water, and are therefore useful for biological monitoring and dye trace studies. Selected excitation and emission filters allow detection of the following substances: chlorophyll-a, coloured dissolved organic matter (CDOM), uranine (fluorescein), rhodamine, phycoerythrin and phycocyanin.

The ECO-FL can operate continuously or periodically and has two different types of connectors to output the data (analogue and RS-232 serial output). The potted optics block results in long term stability of the instrument and the optional anti-biofouling technology delivers truly long term field measurements.

In addition to the standard model, five variants are available, and the differences between these and the basic ECO-FL are listed below:

FL(RT): similar to the FL but operates continuously when power is supplied

FL(RT)D: similar model to the (RT) but has a depth rating of 6000 m

FLB: includes internal batteries for autonomous operation and periodic sampling

FLS: similar to FLB but has an integrated anti-fouling bio-wiper

FLSB: similar to the FLS, but includes internal batteries for autonomous operation

Data Processing

Data were submitted to BODC as 10 ASCII files by SFT and following BODC procedures the data were archived. The files contained all CTD casts from each of the following FRV Scotia cruises: 0215S (49 casts), 0315S (47 casts), 0515S (57 casts), 0815S (32 casts), 1015S (65 casts), 1115S (20 casts), 1315S (125 casts), 1415S (6 casts), 1715S (40 casts) and 1815S (108 casts). The data from cruises 0515S, 1315S and 1815S were also accompanied by a file of quality control flags. The header of each file contained the type of CTD used for each cruise, the sensors on the CTD and their serial numbers, an explanation of the format of the file and details of any calibrations.

The concatenated files were sub-divided into individual files for each cast using in house BODC Matlab software. The divided files were then transferred to BODC internal format using standard BODC processing procedures. The originator's variables were mapped to BODC parameter codes as follows:

Channel derived during transfer using Benson and Krause (1984) if oxygen channel is present.

Channels that were not transferred are available on request.

Screening

Post transfer analysis and crosschecks were applied according to BODC procedures. This involved the screening of data using BODC's in house visualisation software where any suspect data were flagged but not removed.

References

Benson B.B. and Krause D., 1984. The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere. Limnol. Oceanogr., 29(3), 620-632.

Sampling Strategy

During 2015 a number of cruises occurred on the FRV Scotia were objectives covered trawl sampling, fish sampling and hydrographic sampling. As part of the hydrographic sampling numerous CTD casts were completed on each cruise. The time channel of these casts was recorded in GMT.

Data Processing

The CTD data were processed by Marine Scotland using the Sea-Bird SeaSoft routines as recommended in the SeaSoft manual for model type Sea-Bird SBE19plus V2 SEACAT.

Pressure data were binned to 1 dbar using SeaSoft and the primary temperature and conductivity channels were adjusted to produce 'edit' channels. Marine Scotland regards the 'edit' channels as the definitive version of the data.

The adjustments consisted of a de-spiking process using Marine Scotland in-house visualisation software and, as necessary, application of a low pass filter as described in Sy (1985).

Field Calibrations

For a number of the cruises Marine Scotland used water samples collected during the CTD casts to generate a calibration equations for the conductivity and fluorescence channels. However, these calibrations were not applied to the data by the originator.

Fixed Station Information

Station Name

Nolso - Flugga Line

Category

Offshore route/traverse

Nolso-Flugga - Faroe-Shetland Channel section

Long term monitoring carried out by the Marine Laboratory Aberdeen began in the early 1890's by the forerunner of the laboratory, the Fishery Board of Scotland (est. 1882). The first water bottle casts were carried out during 1893 and conducted by Dr H N Dickson on board HMS Jackal. Four of these stations were to become part of the now standard Nolso-Flugga Faroe-Shetland Channel section. In addition, at positions further south, he sampled at three stations and these were to become part of the standard Fair Isle-Munken section. A full set of stations (12) were first sampled along the Nolso-Flugga line in 1903, and since then have more or less been sampled annually or more except for the war years. Since then extra stations have been added to both sections.

Map of standard stations

Nolso-Flugga stations

Listed below are details of the standard hydrographic stations that form the Nolso-Flugga line.

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.